The legislation was introduced in the last session as part of the government's attempt to combat terrorism, to prevent the use of false identities by terrorist and organised crime groups.

The proposals have attracted widespread criticism.

On ideological grounds there is a belief that people should not be beholden to the state in this way.

And practically there is a fear that it may become compulsory to carry the cards and ethnic minorities may be subject to more frequent checks than others.

The Conservatives were officially opposed to the scheme until Michael Howard declared himself in favour on 13 December - much to the chagrin of senior members of his shadow cabinet including Oliver Letwin.